intelligence so far has not detected any signs syria is loading chemical weapons on to aircraft, but defense secretary panetta said it appears the embattled assad regime is preparing to do just that. >> there is no question that we remain very concerned very concerned that as the opposition advances, in particular on damascus that the regime might very well consider the use of chemical weapons. >> reporter: monitoring of syrian basis like this one has pekd up evidence engineers have loaded the chemicals which combine to form the deadly nerve agent sarin into bombs that could be dropped airplanes. satellites have seen trucks moving among want bunkers where the weapons and agents are believed to be stored. u.s. officials say the evidence is strong but circumstantial not definitive. but that combined with fighting infighting in the suburbs of damascus, has led to fears of what the assad regime might do. we asked jeffrey white, a former analyst for the defense intelligence agency, what would happen if the rebels cut off damascus? >> it's the end of the regime. the regime can hang on for